In Hesiod’s Pandora story, the evils were held in a jar, not a box. The Greek term is pithos, a large storage vessel commonly used for commodities such as grain or wine.
The expression “Pandora’s box” became established through later European translations. The Renaissance scholar Erasmus translated pithos with the Latin word pyxis, meaning a box or small container, helping create the familiar modern image.
When Pandora opens the vessel, disease, labor, and other hardships escape into the world. The myth therefore explains why human life contains suffering while also preserving a place for hope.
Artists and popular culture usually depict a hinged box because that image is easy to recognize. It is culturally familiar, but the earliest Greek version specifically describes a large jar.